As a drive apparatus of a hybrid vehicle including an engine, a motor and a generator, an apparatus disclosed, for example, in Patent Document 1 is known. As shown in FIG. 6, the drive apparatus of the hybrid vehicle 100 includes an engine 50, an engine shaft 1 connected to the engine 50 via a crankshaft 51, a motor-generator shaft 2 including an inner shaft 2a connected to the engine shaft 1 via a generator driving gear train 10 and a hollow outer shaft 2b for a motor disposed around the inner shaft 2a, a generator 60 connected to the inner shaft 2a, a motor 70 juxtaposed with the generator 60 and connected to the outer shaft 2b for the motor, an output shaft 3 connected to the outer shaft 2b for the motor via a motor power transmission gear train 20 and disposed parallel to the engine shaft 1 and the motor-generator shaft 2, and a differential device 45 connected to the output shaft 3 via a final gear train 40 and configured to transmit power to driving wheels 47, 47 via a differential shaft 46.
The engine shaft 1 is provided with a clutch 80 to allow or prohibit power transmission between the engine shaft 1 and the output shaft 3 via an engine power transmission gear train 30. As the clutch 80 is opened, a so-called series-drive becomes possible in which the power transmission between the engine shaft 1 and the output shaft 3 is prohibited, the generator 60 generates electricity by the power of the engine 50 and the power obtained by the electricity generation is supplied to the motor 70. Further, as the clutch 80 is engaged, a so-called parallel-drive becomes possible in which the power transmission between the engine shaft 1 and the output shaft 3 is allowed, the power of the engine 50 is transmitted to the output shaft 3 and the power of the motor 70 is transmitted to the output shaft 3.
By the way, in the drive apparatus of the hybrid vehicle disclosed in Patent Document 1 using the generator 60 in order to start the engine 50, there is a problem that the torsional natural vibration frequency of the apparatus itself and the engine torque fluctuation frequency are matched and thus resonance phenomenon occurs when the engine is started and thus excessive torque is applied to the motor-generator shaft 2 or the like. In order to prevent distortion or breakage of the motor-generator shaft 2 or the like due to the resonance phenomenon, there was a need to strengthen the shaft itself.
Meanwhile, in a drive apparatus of a hybrid vehicle disclosed in Patent Document 2 including an engine and a motor, as shown in FIG. 7, a torque limiter mechanism 235 is provided in a damper 230 included in an output shaft 211 of the engine and the power transmission is shut-off by the torque limiter mechanism when the fluctuation torque by the engine and the motor reaches a predetermined value.
Accordingly, in the drive apparatus of the hybrid vehicle disclosed in Patent Document 1, it is also considered that the torque limiter mechanism is provided in the damper included in the output shaft (crankshaft) of the engine in order to prevent the distortion or breakage of the motor-generator shaft 2 or the like due to the resonance phenomenon.